Mohammad Raza Yosufi, the spokesman for Bamyan police said that the girl was raped on Friday in Dost Bek Foladi village of the provincial capital, also Bamyan.
The assault happened as the girl was busy with washing clothesalong the river, he said.
The official said that the culprits fled the area after the assault. The victim was shifted to the hospital and was said to be in stable condition.
Yosufi said that the incident was under serious investigation.